The present invention relates generally to multiprocessor systems, and more specifically to an exclusive access controller for a multiprocessor system.
With prior art hardware-implemented exclusive access controllers employed in multiprocessors, a source processor issues a lock request to the exclusive access controller to cause the processor to make a lock attempt for exclusive access to shared data in the main memory. The firmware of the source processor translates the result of the lock attempt from the exclusive access controller before accessing a common resource stored in the main memory. If the request is not granted in a given attempt, the firmware repeats a lock request until the request is granted. However, shortcomings of this type of exclusive access controller are that (1) complex decoding circuitry is required for interpreting the result of the lock attempt and that (2) the requesting processor must wait a certain period of time before it can access the shared data following a grant of a lock request. All these factors combine to limit the overall efficiency of the multiprocessor system.